Autotransformer



Aug. 30,1921, 1,640,424

- K. K. PALUEFF AUTO TRANSFORMER Filed Jan.v29. 1926 i .i F 2 n Inventor:

Konstantin Kl alueffi His Attorney xous'rnivtrm K.

1,640,424 PATENT OFFICE.

IPALUEFF, F PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

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Application -fi1ed January 29, 1926. Serial No. 84,729.

My invention relates to auto transformers and more particularly to the type of auto transformer having some of its, winding turns provided with tap connections and a tap switch for varying the ratio of voltage transformation. Transformers arranged in this way are often used to interconnect two I transmission lines or systems, the adjustment of the ratioof voltage transformation being used to control the flow of energy between the lines or systems. When a high voltage transient of high frequency or steep wave front enters a terminal atone end of a transformer winding, the inductance-of the winding causes a concentration of voltage in the end turns and extra heavy or buffer insulation is usually provided on these end turns to prevent damage to the winding by the abnormally high voltage. This expedient is not practicable, however, with winding turns which are provided with tap connections because the taps are usually distributed along the winding for some distance and protection for the tap leads and tap switch is also desirable. The general object of the invention is to provide an arrangement of buffer turns which will afford protection for the tap switch, the tap leads and the tapped turns of the winding. Another object of the invention is to arrange these buffer turns so that their presence may not have any objectionable effect on reactance conditions in the main transformer winding, particularly as the switch position is changed from one top to another.

Other objects and advantages will appear from the following description taken in connection with the accompanying drawing in which Fig. 1 is an elevation of an auto transformer embodying the invention and Fig. 2 is an explanatory diagram.

Like reference characters represent similar arts in both figures of the drawing.

The invention is shown in the drawing as embodied in a particular form of auto transformer comprising a shell type magnetic core 10 having av winding leg 11 surrounded by a winding 12. This winding 12 is formed of disc coils which are interleaved in a simple way to reduce reactance although any suitable arrangement of the coils on the core may of course be used.

The transformer is connected to transmit energy between the conductors 13 and 14 of one line and the conductors 15 and 16 of another line. The conductors 13 and 14 of the first line are connected to the two end terminals of the main winding 12 and the conductor 16 of the second line is connected with the conductor 14 to one end of the winding 12. This latter end of the winding 12 and the conductors 14 and 16 are and the conductor 15 is connected to the movable contact-of this tap switch 19 through a protective winding 20 which surrounds the winding leg 11 of the transformer core. By means'of the tap switch, the line conductor 15 may thus be connected through the protective winding 20 to any selected tap on the main winding so as to adjust the ratio of voltage transformation and control the flow of energy through the transformer H as desired.

The purpose of the winding 20 is to provide a few turns with suflicient reactance to protect the tap switch 19 tap leads 18 and tapped portion. of the winding 12 from the effect of abnormal voltage due to high fregueney line transients from the conductor 15.

uch abnormal voltage of high. frequency or steep wave front will be unable to penetrate through this protective winding 20 because of the reactance of the winding. The high voltage may however concentrate in the windin 20 itself so that its turns should be specially protected as by the provision of extra heavy insulation as indicated by heavy lines in Fig. 2.

If the reactance of the winding 20 is appreciable at the normal frequency of'operation of the transformer, thereactance relations of the line circuits will be changed as the tap connections are changed b the switch 19 and this is sometimes undeslrable. This may be avoided without destroying the protective function of the winding 20 by arranging and connecting the turns IOU l of this winding so that part of them preferably one half, conduct current about the core in a direction opposite to that of the current in the remainder of the turns. The reactance of the winding 20 may thus be small or negligible for the normal operating frequency of the transformer. The reactance will be sufficient however to give the desired protection against line transients because it increases rapidly with the frequency and the frequency of a transient is extremely high.

A specific form of the invention having been described, various modifications within thescope of the appended claims will be obvious.

What I claim as new and desire to secure by Letters Patent of the United States, .is:

1. An auto transformer comprising a core, a main winding and a protective winding on said core, said main Wmding having a plurality of taps, and a tap switch connected between said protective winding and said taps, whereby a line conductor may be connected through said protective winding to any selected tap.

2. An auto transformer comprising a core, a main winding and a protective winding on said core, said main winding having a plurality of taps, and a tap switch connected between said protective winding and said taps, whereby a line conductor may be connected through said protective winding to i any selected tap, said protective winding having part of its turns arranged and connected to conduct current in a direction about said core opposite to that of the current in the remainder of its turns.

In witness whereof, I have hereunto set my hand this 26th day of January, 1926.

KONSTANTIN K. PALUEFF. 

